This disclosure relates to bicycle wheel hubs, and specifically the freewheel mounts for the rear hub and sprocket. It is an advance of some of the concepts set forth by the inventor n U.S. Pat. No. 4,154,327 issued May 15, 1979 for a CONVERTIBLE BICYCLE HUB, and sets forth additional features not considered in that patent.
The bicycle has evolved enormously over the years, and many of its components have become increasingly sophisticated. However, in some respects this has been disadvantageous insofar as increasing sophistication in different directions by different manufacturers has resulted in increasing incompatibility between parts.
In the field of wheel hubs, many manufacturers have their own hub systems which are incompatible with one another, so that a freewheel for one make of bicycle will not work with the hubs of another manufacturer. To make matters worse, most manufacturers have their own specially designed tool that is required to remove the freewheel, and the tool cannot be used on other freewheels. Since riding the bicycle exerts continuous and extreme tightening force at the threaded interconnection, it is difficult or impossible to remove the freewheel with generic tools.
Additionally, generally speaking the front hub of the bicycle cannot be used interchangeably with the rear hub, and the rear hub cannot be reversed, at least not without changing the size of the freewheel mount such as can be done on the so-called "flip-flop" system in which extension collars of different diameters extend from the opposite ends of the hub.
Aside from the incompatibility problem, typically the freewheel assembly of current model BMX racing bicycles mounts a single gear sprocket which is integral with the freewheel assembly. In order to replace the sprocket, for example with one having a different number of teeth, the entire freewheel must be changed. Also, the freewheel mechanism of BMX bicycles generally will not mount more than a single sprocket at a time.
An additional and even more vexing problem is the universal manner in which the freewheel mechanism of current designs is mounted to the hub. In all instances, the hub has a unitary extension sleeve which is externally threaded to accept the freewheel, which is screwed onto the sleeve and increasingly tightens as the freewheel is torqued during bicycle use.
With BMX bicycles used for competitive racing, the stress on the threaded freewheel mounting shaft of the hub, as well the interior threads of the freewheel assembly, is enormous. This leads to frequent stripping of the threads and even breaking of chunks of the sleeve or freewheel mechanism during the most intensive parts of these competitions. In some instances, the threaded freewheel mount also renders the hub unusable as a front hub.
Concerning the bearing mountings on most bicycles, typically the ball bearings of at least one of the two axle bearing rings are retained on the axially outer side by an annular retainer held against the loose bearings by a nut on the axle. The bearings are thus in the compressive force line of the hub mount, and the over- or under-tightening of the nut during assembly or in use can either grind the bearings into the ball races, or create play in the bearing set.
The annular bearing sets are also typically axially outside the main portion of the hub in a hub extension, with the freewheel being threadedly mounted on the extension so that the freewheel axially overlaps the bearings. This requires the freewheel to be large enough in diameter to fit over the bearings, which in turn limits the minimum size of the sprocket that can be used on the freewheel, which is generally a 15-tooth sprocket, although with a specially designed freewheel a 14-tooth sprocket can be used.